The Effects of Chronic Right Hemispheric Damage on the Allocation of Spatial Attention: Alterations of Accuracy and Reliability.

Right hemispheric damage (RHD) caused by strokes often induce attentional disorders such as hemispatial neglect. Most patients with neglect over time have a reduction in their ipsilesional spatial attentional bias. Despite this improvement in spatial bias, many patients remain disabled. The cause of this chronic disability is not fully known, but even in the absence of a directional spatial attentional bias, patients with RHD may have an impaired ability to accurately and precisely allocate their spatial attention. This inaccuracy and variable directional allocation of spatial attention may be revealed by repeated performance on a spatial attentional task, such as line bisection (LBT). Participants with strokes of their right versus left (LHD) hemisphere along with healthy controls (HC) performed 24 consecutive trials of 24 cm horizontal line bisections. A vector analysis of the magnitude and direction of deviations from midline, as well as their standard deviations (SD), were calculated. The results demonstrated no significant difference between the LHD, RHD and HC groups in overall spatial bias (mean bisection including magnitude and direction); however, the RHD group had a significantly larger variability of their spatial errors (SD), and made larger errors (from midline) than did the LHD and HC groups. There was a curvilinear relationship between the RHD participants' performance variability and their severity of their inaccuracy. Therefore, when compared to HC and LHD, the RHD subjects' performance on the LBT is more variable and inaccurate.

Dopamine does not appear to affect mental rotation in Parkinson's disease.

OBJECTIVE: Patients with Parkinson's disease (PD) often have deficits with mental rotation (MR). The neuropathological factors underlying these deficits, however, remain to be elucidated. One hypothesis suggests that dopamine depletion in nigro-striatal systems adversely influences MR. Another hypothesis suggests that deterioration of cortical (fronto-temporo-parietal basal ganglia) networks that mediate this function are responsible for this deficit. The goal of this study was to test the dopamine hypothesis by determining if dopamine abstinence negatively influences MR performance. METHODS: Thirty three non-demented right-handed individuals with PD were assess for their ability to perform a pencil and paper MR test while "on" and "off" dopaminergic medications. Dopamine abstinence followed the typical overnight withdrawal procedures. RESULTS: No differences in mental rotation abilities were found between "on" and "off" dopaminergic medications. CONCLUSIONS: These results suggest that other neuropathological factors, such as cortical-basal ganglia neurodegeneration, or dysfunction of other neurotransmitters systems, might account for these cognitive deficits and future research will have to test these alternative hypotheses.

The influence of emotional faces on the spatial allocation of attention.

OBJECTIVES: Studies suggest that the right hemisphere is dominant for emotional facial recognition. In addition, whereas some studies suggest the right hemisphere mediates the processing of all emotions (dominance hypothesis), other studies suggest that the left hemisphere mediates positive emotions the right mediates negative emotions (valence hypothesis). Since each hemisphere primarily attends to contralateral space, the goals of this study was to learn if emotional faces would induce a leftward deviation of attention and if the valence of facial emotional stimuli can influence the normal viewer's spatial direction of attention. METHODS: Seventeen normal right handed participants were asked to bisect horizontal lines that had all combinations of sad, happy or neutral faces at ends of these lines. During this task the subjects were never requested to look at these faces and there were no task demands that depended on viewing these faces. RESULTS: Presentation of emotional faces induced a greater leftward deviation compared to neutral faces, independent of where (spatial position) these faces were presented. However, faces portraying negative emotions tended to induce a greater leftward bias than positive emotions. CONCLUSIONS: Independent of location, the presence of emotional faces influenced the spatial allocation of attention, such that normal subjects shift the direction of their attention toward left hemispace and this attentional shift appears to be greater for negative (sad) than positive faces (happy).

Frontal-executive constructional apraxia: when delayed recall is better than copying.

UNLABELLED: In assessments of visuospatial function and memory, patients are often required to copy a figure and later to reproduce that figure from memory. Whereas most people perform better on a copying task than when drawing from memory, in this study we describe an unusual pattern of performance in which patients are better at drawing from memory than copying. Consecutive patients in a neurocognitive disorders clinic were given a battery of clinical cognitive tests that included copying a figure of intersecting pentagons and then drawing the figure from memory. Patterns of drawing performance at the two time points were compared to the profile of other cognitive deficits. RESULTS: A subgroup of four patients with frontal dysfunction showed marked improvement in drawings at a delay compared to copying. Prior studies have indicated that most patients have declines in drawing performance at a delay. The unusual pattern of better performance at a delay compared to an initial copy occurred in patients with frontal dysfunction. These patients' visuoconstructive deficit and subsequent improvement could be related to either a failure to disengage when a model is present, to memory consolidation with increased reliance on top-down processing in the delay condition, or to relative preservation of global versus local aspects of a stimulus in memory. The addition of a task to assess drawing after a delay to a standard clinical screening battery such as the Mini-Mental Status Examination (MMSE) provides the opportunity to evaluate this phenomenon that may be indicative of frontal-executive dysfunction.

Working memory in Parkinson's disease: the effects of depression and side of onset of motor symptoms.

OBJECTIVE: Previous research has examined the neurocognitive effects of depression in Parkinson's disease (PD), finding worse performance on tests of cognitive functioning in PD patients with depression as compared to those without depression. However, this research has not considered the effect of side of onset of motor symptoms. Hence, we sought to investigate the interaction between depression and side of onset on working memory in patients with PD. METHOD: A total of 66 patients with PD completed the Digit Span Backward subtest of the Wechsler Memory Scale-III as well as two other tests of executive functioning. Groups of left hemibody onset (LHO) with and without depression and right hemibody onset (RHO) with and without depression were created. RESULTS: The results indicated significantly lower performance on the measure of working memory for the LHO with depression group, relative to both the LHO without depression and the RHO with depression groups. CONCLUSION: These findings indicate that working memory is worse in patients with LHO of motor symptoms who are also depressed, and they suggest that this group of patients might experience greater disability and lower quality of life.

Mood disturbances and cognitive functioning in Parkinson's disease: the effects of disease duration and side of onset of motor symptoms.

Some research has supported differences in mood functioning in patients with Parkinson's disease (PD) whose motor symptoms begin at the left or right hemibody. Also, a relationship between disease duration and mood disturbances has been reported, but only for PD patients with right hemibody onset. There have been no investigations reported examining the potential interactions between side of onset of motor symptoms, mood, and disease duration on cognitive functioning. Hence, the purpose of this investigation was to determine whether the interaction between mood and disease duration differentially affects cognitive functioning in patients with PD whose motor symptoms begin at the left and right hemibody. A total of 33 PD patients with left hemibody onset and 29 PD patients with right hemibody onset were given a battery of tests to evaluate mood functioning and general cognitive functioning. As predicted, the results indicated that the interaction of disease duration and mood significantly predicted cognitive functioning for PD patients with right hemibody onset of symptoms but not for PD patients with left hemibody onset of symptoms. Interestingly, an unexpected finding was a significant positive relationship between disease duration and energy level for patients with left hemibody onset but not for patients with right hemibody onset. These results indicate that mood problems and disease duration interact to significantly affect cognitive functioning but only for those PD patients who experience a right hemibody onset of symptoms.

Anxiety and depression severity are related to right but not left onset Parkinson's disease duration.

Depression and anxiety have both been associated with relative left frontal hypoactivation and the motor symptoms of Parkinson's disease typically begin in a lateral or asymmetrical fashion. Hence, PD patients with right hemibody onset may experience heightened depression and anxiety. However, research is mixed regarding whether right or left hemibody onset PD is associated with elevated levels of depression and anxiety. This literature, though, has not considered the potential moderating variable of disease duration. We hypothesized that disease duration would be positively correlated with measures of depression and anxiety in right but not left hemibody onset PD patients. The results indicated that scores on the Geriatric Depression Scale, Beck Depression Inventory-II, and the State Trait Anxiety Scale - State correlated positively with disease duration, but only in the right hemibody onset group of PD patients. Thus, right hemibody onset PD is associated with more severe depressive and anxiety symptoms, but only when disease duration is considered.

Influence of left versus right hemibody onset Parkinson's disease on cardiovascular control.

Whereas the left hemisphere is involved in regulating the parasympathetic nervous system, the right hemisphere regulates the sympathetic. Given the asymmetrical onset of motor symptoms and neuropathology in PD, differences in cardiovascular functions might be expected between PD patients with left hemibody onset (LHO) versus right hemibody onset (RHO). A total of 66 PD patients served as participants, including 31 LHO patients and 35 RHO PD patients. All participants had their resting heart rate (HR) and blood pressure (BP) recorded. Although the LHO group had lower systolic BP, it had higher resting HR than did the RHO group. The reason for this dissociation is not known but might be related to asymmetrical vagus nerve control of the heart (SA node). Future researchers might want to use additional indices of cardiovascular functioning that are more precise measures of parasympathetic and sympathetic functioning, as well as learn the influence of dopaminergic medications.

Verbal and visuospatial memory in lateral onset Parkinson disease: time is of the essence.

OBJECTIVE: This investigation sought to study immediate and delayed verbal and visuospatial recall in Parkinson disease (PD) patients with left hemibody (LHO) and right hemibody (RHO) onset of motor symptoms and to examine the role of mental processing speed in recall of this information. BACKGROUND: Research is mixed regarding material specific memory impairments in LHO and RHO PD. However, earlier research has not used a factorial approach in investigating material specific memory in LHO and RHO PD. We hypothesized that LHO PD patients would exhibit an increase in performance following the delayed verbal free recall trial and either decline or stability in performance on the delayed visuospatial free recall trial. The opposite pattern was hypothesized for RHO PD patients. METHOD: The Hopkins Verbal Learning Test-revised (HVLT-R) and the Brief Visuospatial Memory Test-revised (BVMT-R) were administered to a sample of 28 LHO PD patients and 36 RHO PD patients. The Stroop Color-word Test was administered as a measure of mental processing speed. RESULTS: The results indicated that the RHO group experienced a significant decline in performance on verbal free recall from the immediate to the delayed trials and a significant improvement in performance from the immediate to the delayed visuospatial free recall trials. Additionally, a significant negative correlation was found between mental processing speed and changes in recall from the immediate to the delayed conditions for the RHO group. CONCLUSIONS: These results indicate that the RHO PD group experienced a significant decline in verbal free recall and a significant improvement in visuospatial free recall from the immediate to the delayed trials and that the LHO PD patients experienced no significant changes. Further, mental processing speed appears to influence the recall of information from the immediate to the delayed conditions.

Visual-spatial disembedding in Parkinson's disease.

Visual-spatial disembedding requires a person to visually scan the stimulus and allocate spatial selective attention to the locations of relevant stimuli. Parkinson's disease (PD) is often associated with visual-spatial deficits, but the influence of PD on disembedding is not entirely known. The goal of this study is to learn whether participants with PD have defective visuospatial disembedding and whether this defect responds to dopaminergic treatment. We also wanted to examine the relationship of disembedding with other cognitive processes and the different parkinsonian clinical symptoms. Participants were PD patients and matched controls. PD participants were tested "on" and "off" medications on the Hidden Patterns Test (HPT) and tests of frontal-executive functions. PD patients had difficulties in visual-spatial disembedding that were not related to medication status, illness duration or severity, or symptom presentation, but were related to other tasks requiring visual scanning in response to alterations in spatial allocation of attention. Lack of improvement with dopaminergic treatment suggests deficits in other neurotransmitter-neuromodulatory systems or degenerative processes in the frontal-striatal networks, cortex, or basal ganglia.

Verbal learning in Alzheimer's disease: cumulative word knowledge gains across learning trials.

Research regarding learning in Alzheimer's disease (AD) patients has been mixed. Learning capacity might be better indexed using a score that reflects the interaction between the learning slope and total recall, referred to as the Cumulative Word Learning (CWL) score. We compared a group of AD patients to normal participants using a traditional index of learning and the CWL score that were derived from the Hopkins Verbal Learning Test-Revised (HVLT-R). The HVLT-R is a supra-span, list-learning test containing 12 words from three semantic categories. The results indicated that the sample of AD patients performed within the average range, using the traditional learning z score. Although mild AD patients were not found to differ from controls in the traditional learning z score, a significant difference was noted for the CWL score. The moderate AD patients differed from the normal controls in both learning measures. Furthermore, unlike the traditional learning score, the CWL score was a significant predictor of overall cognitive functioning, as indexed using their Mini-Mental State Examination (MMSE) score. Thus, the CWL score might be a more sensitive indicator overall of total learning capacity and may be useful in staging Alzheimer's disease because of increased resilience to floor effects.

Virtual reality rehabilitation of spatial abilities after brain damage.

Current rehabilitation of navigation and spatial orientation ability after brain damage is generally focused on training within the rehabilitation hospital or the patient's home as part of common physio- and occupational therapy sessions. To further promote generalization of gained abilities and to quantify functional improvements, this project aims at developing a Virtual Reality (VR) application that can be used for training and assessment of spatial orientation and navigation skills in brain-damaged patients. The training is administered after the standard hospital rehabilitation training is completed. Additionally, the program will be used as an assessment tool to quantify the participants' wayfinding performance. The data will be compared with real-world navigation performance in tasks of similar complexity to evaluate real-world transfer of the VR training. Currently, the application is under development and basic functionality and data acquisition are being implemented.

Greater motor improvement in right hemibody Parkinson's patients after dopaminergic medications.

Due to motor and neuropathological asymmetries, Parkinson's disease (PD) patients with right hemibody onset (RHO) of symptoms may experience greater benefit from dopaminergic enhancing medications, relative to patients with left hemibody onset (LHO). We investigated this possibility by measuring UPDRS scores of 20 PD patients with LHO and 13 patients with RHO, both prior and subsequent to taking dopaminergic enhancing medications. Following treatment, the motor score from the UPDRS improved for both groups of patients. However, PD patients with RHO experienced greater improvement in motor functioning following administration of dopaminergic enhancing medications than those with LHO.

A brief computerized self-screen for dementia.

Among his many contributions to the field of neuropsychology, Arthur Benton recognized the broad public health significance and unique ability of focused neuropsychological tests to screen for dementia. The need for validated screening tests for the presence of dementia will continue to grow as the cumulative prevalence of dementia grows and as our ability to treat or slow the progression of these diseases improves. We have developed a brief, self-administered computerized screening test for dementia, which is user friendly to the majority of elderly participants, including those with dementia. This test demonstrates comparable discriminant validity to the Mini Mental State Examination (MMSE), and its subscales correlate well with the traditional neuropsychological tests upon which it is based. We discuss its relative merits and limitations in comparison to other current instruments as well as suggesting future directions for this field.

Age-related changes in arm-hand postural knowledge.

Cognitive changes have been reported during healthy ageing, but there have been no investigations of older people's knowledge of transitive and intransitive forelimb postures and movements. A total of 18 healthy elderly participants in two age groups, old (66-76 years) and older (77-88 years), all of whom performed normally on the Mini-Mental Status Examination (MMSE) and Boston Naming Test (BNT), performed a transitive and intransitive gesture postural discrimination test. Whereas there were no significant differences between the two groups in education or performance on the MMSE and BNT, the older group performed significantly worse on both transitive and intransitive posture recognition with more errors in the recognition of transitive than in the recognition of intransitive postures. However, the recognition of both transitive and intransitive declined with age at a similar rate. These results support the hypothesis that, with ageing, there is a decrement in the brain systems important in the recognition of transitive and intransitive posture.

Effects of donepezil on verbal memory after semantic processing in healthy older adults.

OBJECTIVE: To learn if acetylcholinesterase inhibitors alter verbal recall by improving semantic encoding in a double-blind randomized placebo-controlled trial. BACKGROUND: Cholinergic supplementation has been shown to improve delayed recall in adults with Alzheimer disease. With functional magnetic resonance imaging, elderly adults, when compared with younger participants, have reduced cortical activation with semantic processing. There have been no studies investigating the effects of cholinergic supplementation on semantic encoding in healthy elderly adults. METHOD: Twenty elderly participants (mean age 71.5, SD+/-5.2) were recruited. All underwent memory testing before and after receiving donepezil (5 mg, n=11 or 10 mg, n=1) or placebo (n=8) for 6 weeks. Memory was tested using a Levels of Processing task, where a series of words are presented serially. Subjects were either asked to count consonants in a word (superficially process) or decide if the word was "pleasant" or "unpleasant" (semantically process). RESULTS: After 6 weeks of donepezil or placebo treatment, immediate and delayed recall of superficially and semantically processed words was compared with baseline performance. Immediate and delayed recall of superficially processed words did not show significant changes in either treatment group. With semantic processing, both immediate and delayed recall performance improved in the donepezil group. CONCLUSIONS: Our results suggest that when using semantic encoding, older normal subjects may be aided by anticholinesterase treatment. However, this treatment does not improve recall of superficially encoded words.

Spatial attentional bias in normal people: object or viewer-centered.

When bisecting radial lines, normal subjects often have a distal bias. To help in explaining this systematic bias, it has been proposed that normal people have an attentional bias to the top of the lines (object centered hypothesis) or toward stimuli falling in the lower portion of the retina (retinotopic hypotheses) or to distal peripersonal space (body centered hypotheses). The primary aim of this study is to test these hypotheses by having normal subjects bisect radial lines, placed in a clockwise distribution in the transverse plane, below eye level. Our results demonstrate that the perception of the midpoint progressively changes as a function of the body centered orientation of the lines, with subjects demonstrating a progressively greater distal bias as they approached the midsagittal plane or radial condition. These findings provide support for the postulate that distal bias on radial lines bisections is body centered.

Reduced verbal learning associated with posterior temporal lobe slow wave activity.

Functional imaging has revealed that during verbal-word learning there is activation of the left posterior temporo-parietal region (PTPL). The purpose of this study was to learn if differences in the ability of normal people to learn might be accounted for by differences in electrophysiological (EEG) measures of activation of their left, but not right, PTPL. The Rey Auditory Verbal Learning Test (RAVLT) was administered to 42 men without neurological diseases. Delta magnitude, as measured by quantitative electroencephalography (QEEG), was recorded from the left and right PTPL while the participants sat quietly with their eyes closed. The magnitude of delta EEG activity is inversely proportional to cerebral activation. Based on delta magnitude, comparison groups were created by separating those with low and high delta at the left and right PTPL. Cumulative word learning (CWL) on the RAVLT was computed by subtracting the number of words recalled on the first learning trial from the highest number of words recalled on the fourth or fifth trial and multiplying this difference by the total words recalled during all 5 learning trials. The group with a greater magnitude of left PTPL delta activity had a significantly poorer CWL scores than those with less delta, but the CWL scores of the group with a greater magnitude of delta of the right PTPL was no different that the group with less right-sided delta. No significant differences emerged at any frontal or parietal electrode site. Decreased activation of the left, but not right, PTPL appears to be associated with a decreased verbal leaning ability.

Spreading activation of lexical-semantic networks in Parkinson's disease.

Although dopamine may act as a neuromodulator of spreading activation within semantic networks, this role of dopamine in lexical networks has not been investigated. Hence, we sought to investigate the effects of Parkinson's disease (PD), which is associated with dopamine depletion, on spreading activation in the lexical networks. Ten Parkinson's disease patients and 11 normal controls performed the controlled oral word association test and the average word frequency for their responses was calculated and used as an index of spreading activation. The PD patients exhibited a lower average word frequency, suggesting increased spreading activation, and a significant relationship between the strength of the initial activation and subsequent extent of spreading activation. Most patients were taking dopaminergic medication and future studies may benefit from examining the changes in spreading activation in lexical networks in PD patients on versus off medication or in healthy controls taking either a placebo or a dopaminergic medication. Although these alterations in lexical access might be related to the reduction of dopamine, one of the hallmarks of PD, these patients also have alterations of other neurotransmitter systems and further studies are needed to more clearly identify the role played by these neurotransmitter on lexical access.

Emotional influences on spatial attention.

The relationships between the anterior-posterior and left-right regions of the brain have been characterized as mutually inhibitory. Whereas the left hemisphere attends to right proximal hemispace and is associated with positive emotions, the right hemisphere attends to left distal hemispace and is associated with negative emotions. Because of the excitatory and inhibitory influences between the left and right frontal and posterior regions of the brain, the expression of emotion will result in an ipsilateral attentional bias. Given these functional systems, we hypothesized that positive emotions would be associated with a bias for left distal hemispace and negative emotions would be associated with a bias for right proximal hemispace. We tested these hypotheses by having 138 undergraduate students place emotionally labeled pegs on a large board. Our results indicated that the positively labeled pegs were placed in left distal hemispace and the relative placement of negatively labeled pegs was rightward and proximally. Whereas numerous research investigations have examined how attention is biased for emotional stimuli, ours is the first investigation to provide evidence that emotions can bias attentional allocation.